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Revision: 1.11
Committed: Sat Nov 24 07:14:26 2007 UTC (16 years, 5 months ago) by root
Branch: MAIN
Changes since 1.10: +103 -19 lines
Log Message:
enhance documentation, also typedef all watcher types (doh, can't do this for ev_loop :()

File Contents

# User Rev Content
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131     .IX Title ""<STANDARD INPUT>" 1"
132 root 1.10 .TH "<STANDARD INPUT>" 1 "2007-11-24" "perl v5.8.8" "User Contributed Perl Documentation"
133 root 1.1 .SH "NAME"
134     libev \- a high performance full\-featured event loop written in C
135     .SH "SYNOPSIS"
136     .IX Header "SYNOPSIS"
137     .Vb 1
138     \& #include <ev.h>
139     .Ve
140     .SH "DESCRIPTION"
141     .IX Header "DESCRIPTION"
142     Libev is an event loop: you register interest in certain events (such as a
143     file descriptor being readable or a timeout occuring), and it will manage
144     these event sources and provide your program with events.
145     .PP
146     To do this, it must take more or less complete control over your process
147     (or thread) by executing the \fIevent loop\fR handler, and will then
148     communicate events via a callback mechanism.
149     .PP
150     You register interest in certain events by registering so-called \fIevent
151     watchers\fR, which are relatively small C structures you initialise with the
152     details of the event, and then hand it over to libev by \fIstarting\fR the
153     watcher.
154     .SH "FEATURES"
155     .IX Header "FEATURES"
156     Libev supports select, poll, the linux-specific epoll and the bsd-specific
157     kqueue mechanisms for file descriptor events, relative timers, absolute
158     timers with customised rescheduling, signal events, process status change
159     events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event
160     loop mechanism itself (idle, prepare and check watchers). It also is quite
161     fast (see this benchmark comparing
162     it to libevent for example).
163     .SH "CONVENTIONS"
164     .IX Header "CONVENTIONS"
165     Libev is very configurable. In this manual the default configuration
166     will be described, which supports multiple event loops. For more info
167     about various configuration options please have a look at the file
168     \&\fI\s-1README\s0.embed\fR in the libev distribution. If libev was configured without
169     support for multiple event loops, then all functions taking an initial
170     argument of name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR)
171     will not have this argument.
172     .SH "TIME REPRESENTATION"
173     .IX Header "TIME REPRESENTATION"
174     Libev represents time as a single floating point number, representing the
175     (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
176     the beginning of 1970, details are complicated, don't ask). This type is
177     called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
178 root 1.9 to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
179     it, you should treat it as such.
180 root 1.1 .SH "GLOBAL FUNCTIONS"
181     .IX Header "GLOBAL FUNCTIONS"
182     These functions can be called anytime, even before initialising the
183     library in any way.
184     .IP "ev_tstamp ev_time ()" 4
185     .IX Item "ev_tstamp ev_time ()"
186 root 1.2 Returns the current time as libev would use it. Please note that the
187     \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp
188     you actually want to know.
189 root 1.1 .IP "int ev_version_major ()" 4
190     .IX Item "int ev_version_major ()"
191     .PD 0
192     .IP "int ev_version_minor ()" 4
193     .IX Item "int ev_version_minor ()"
194     .PD
195     You can find out the major and minor version numbers of the library
196     you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
197     \&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
198     symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
199     version of the library your program was compiled against.
200     .Sp
201     Usually, it's a good idea to terminate if the major versions mismatch,
202     as this indicates an incompatible change. Minor versions are usually
203     compatible to older versions, so a larger minor version alone is usually
204     not a problem.
205 root 1.9 .Sp
206     Example: make sure we haven't accidentally been linked against the wrong
207     version:
208     .Sp
209     .Vb 3
210     \& assert (("libev version mismatch",
211     \& ev_version_major () == EV_VERSION_MAJOR
212     \& && ev_version_minor () >= EV_VERSION_MINOR));
213     .Ve
214 root 1.6 .IP "unsigned int ev_supported_backends ()" 4
215     .IX Item "unsigned int ev_supported_backends ()"
216     Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR
217     value) compiled into this binary of libev (independent of their
218     availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for
219     a description of the set values.
220 root 1.9 .Sp
221     Example: make sure we have the epoll method, because yeah this is cool and
222     a must have and can we have a torrent of it please!!!11
223     .Sp
224     .Vb 2
225     \& assert (("sorry, no epoll, no sex",
226     \& ev_supported_backends () & EVBACKEND_EPOLL));
227     .Ve
228 root 1.6 .IP "unsigned int ev_recommended_backends ()" 4
229     .IX Item "unsigned int ev_recommended_backends ()"
230     Return the set of all backends compiled into this binary of libev and also
231     recommended for this platform. This set is often smaller than the one
232     returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
233     most BSDs and will not be autodetected unless you explicitly request it
234     (assuming you know what you are doing). This is the set of backends that
235 root 1.8 libev will probe for if you specify no backends explicitly.
236 root 1.10 .IP "unsigned int ev_embeddable_backends ()" 4
237     .IX Item "unsigned int ev_embeddable_backends ()"
238     Returns the set of backends that are embeddable in other event loops. This
239     is the theoretical, all\-platform, value. To find which backends
240     might be supported on the current system, you would need to look at
241     \&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
242     recommended ones.
243     .Sp
244     See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
245 root 1.1 .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
246     .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
247     Sets the allocation function to use (the prototype is similar to the
248     realloc C function, the semantics are identical). It is used to allocate
249     and free memory (no surprises here). If it returns zero when memory
250     needs to be allocated, the library might abort or take some potentially
251     destructive action. The default is your system realloc function.
252     .Sp
253     You could override this function in high-availability programs to, say,
254     free some memory if it cannot allocate memory, to use a special allocator,
255     or even to sleep a while and retry until some memory is available.
256 root 1.9 .Sp
257     Example: replace the libev allocator with one that waits a bit and then
258     retries: better than mine).
259     .Sp
260     .Vb 6
261     \& static void *
262     \& persistent_realloc (void *ptr, long size)
263     \& {
264     \& for (;;)
265     \& {
266     \& void *newptr = realloc (ptr, size);
267     .Ve
268     .Sp
269     .Vb 2
270     \& if (newptr)
271     \& return newptr;
272     .Ve
273     .Sp
274     .Vb 3
275     \& sleep (60);
276     \& }
277     \& }
278     .Ve
279     .Sp
280     .Vb 2
281     \& ...
282     \& ev_set_allocator (persistent_realloc);
283     .Ve
284 root 1.1 .IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
285     .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
286     Set the callback function to call on a retryable syscall error (such
287     as failed select, poll, epoll_wait). The message is a printable string
288     indicating the system call or subsystem causing the problem. If this
289     callback is set, then libev will expect it to remedy the sitution, no
290     matter what, when it returns. That is, libev will generally retry the
291     requested operation, or, if the condition doesn't go away, do bad stuff
292     (such as abort).
293 root 1.9 .Sp
294     Example: do the same thing as libev does internally:
295     .Sp
296     .Vb 6
297     \& static void
298     \& fatal_error (const char *msg)
299     \& {
300     \& perror (msg);
301     \& abort ();
302     \& }
303     .Ve
304     .Sp
305     .Vb 2
306     \& ...
307     \& ev_set_syserr_cb (fatal_error);
308     .Ve
309 root 1.1 .SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
310     .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
311     An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two
312     types of such loops, the \fIdefault\fR loop, which supports signals and child
313     events, and dynamically created loops which do not.
314     .PP
315     If you use threads, a common model is to run the default event loop
316     in your main thread (or in a separate thread) and for each thread you
317     create, you also create another event loop. Libev itself does no locking
318     whatsoever, so if you mix calls to the same event loop in different
319     threads, make sure you lock (this is usually a bad idea, though, even if
320     done correctly, because it's hideous and inefficient).
321     .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4
322     .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"
323     This will initialise the default event loop if it hasn't been initialised
324     yet and return it. If the default loop could not be initialised, returns
325     false. If it already was initialised it simply returns it (and ignores the
326 root 1.6 flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards).
327 root 1.1 .Sp
328     If you don't know what event loop to use, use the one returned from this
329     function.
330     .Sp
331     The flags argument can be used to specify special behaviour or specific
332 root 1.8 backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
333 root 1.1 .Sp
334 root 1.8 The following flags are supported:
335 root 1.1 .RS 4
336     .ie n .IP """EVFLAG_AUTO""" 4
337     .el .IP "\f(CWEVFLAG_AUTO\fR" 4
338     .IX Item "EVFLAG_AUTO"
339     The default flags value. Use this if you have no clue (it's the right
340     thing, believe me).
341     .ie n .IP """EVFLAG_NOENV""" 4
342     .el .IP "\f(CWEVFLAG_NOENV\fR" 4
343     .IX Item "EVFLAG_NOENV"
344     If this flag bit is ored into the flag value (or the program runs setuid
345     or setgid) then libev will \fInot\fR look at the environment variable
346     \&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
347     override the flags completely if it is found in the environment. This is
348     useful to try out specific backends to test their performance, or to work
349     around bugs.
350 root 1.6 .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
351     .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
352     .IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
353 root 1.3 This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
354     libev tries to roll its own fd_set with no limits on the number of fds,
355     but if that fails, expect a fairly low limit on the number of fds when
356     using this backend. It doesn't scale too well (O(highest_fd)), but its usually
357     the fastest backend for a low number of fds.
358 root 1.6 .ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
359     .el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
360     .IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
361 root 1.3 And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than
362     select, but handles sparse fds better and has no artificial limit on the
363     number of fds you can use (except it will slow down considerably with a
364     lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
365 root 1.6 .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
366     .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
367     .IX Item "EVBACKEND_EPOLL (value 4, Linux)"
368 root 1.3 For few fds, this backend is a bit little slower than poll and select,
369     but it scales phenomenally better. While poll and select usually scale like
370     O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
371     either O(1) or O(active_fds).
372     .Sp
373     While stopping and starting an I/O watcher in the same iteration will
374     result in some caching, there is still a syscall per such incident
375     (because the fd could point to a different file description now), so its
376     best to avoid that. Also, \fIdup()\fRed file descriptors might not work very
377     well if you register events for both fds.
378 root 1.7 .Sp
379     Please note that epoll sometimes generates spurious notifications, so you
380     need to use non-blocking I/O or other means to avoid blocking when no data
381     (or space) is available.
382 root 1.6 .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
383     .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
384     .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
385 root 1.3 Kqueue deserves special mention, as at the time of this writing, it
386     was broken on all BSDs except NetBSD (usually it doesn't work with
387     anything but sockets and pipes, except on Darwin, where of course its
388 root 1.8 completely useless). For this reason its not being \*(L"autodetected\*(R"
389     unless you explicitly specify it explicitly in the flags (i.e. using
390     \&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR).
391 root 1.3 .Sp
392     It scales in the same way as the epoll backend, but the interface to the
393     kernel is more efficient (which says nothing about its actual speed, of
394     course). While starting and stopping an I/O watcher does not cause an
395     extra syscall as with epoll, it still adds up to four event changes per
396     incident, so its best to avoid that.
397 root 1.6 .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
398     .el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
399     .IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
400 root 1.3 This is not implemented yet (and might never be).
401 root 1.6 .ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
402     .el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
403     .IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
404 root 1.3 This uses the Solaris 10 port mechanism. As with everything on Solaris,
405     it's really slow, but it still scales very well (O(active_fds)).
406 root 1.7 .Sp
407     Please note that solaris ports can result in a lot of spurious
408     notifications, so you need to use non-blocking I/O or other means to avoid
409     blocking when no data (or space) is available.
410 root 1.6 .ie n .IP """EVBACKEND_ALL""" 4
411     .el .IP "\f(CWEVBACKEND_ALL\fR" 4
412     .IX Item "EVBACKEND_ALL"
413 root 1.4 Try all backends (even potentially broken ones that wouldn't be tried
414     with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
415 root 1.6 \&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.
416 root 1.1 .RE
417     .RS 4
418 root 1.3 .Sp
419     If one or more of these are ored into the flags value, then only these
420     backends will be tried (in the reverse order as given here). If none are
421     specified, most compiled-in backend will be tried, usually in reverse
422     order of their flag values :)
423 root 1.8 .Sp
424     The most typical usage is like this:
425     .Sp
426     .Vb 2
427     \& if (!ev_default_loop (0))
428     \& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
429     .Ve
430     .Sp
431     Restrict libev to the select and poll backends, and do not allow
432     environment settings to be taken into account:
433     .Sp
434     .Vb 1
435     \& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
436     .Ve
437     .Sp
438     Use whatever libev has to offer, but make sure that kqueue is used if
439     available (warning, breaks stuff, best use only with your own private
440     event loop and only if you know the \s-1OS\s0 supports your types of fds):
441     .Sp
442     .Vb 1
443     \& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
444     .Ve
445 root 1.1 .RE
446     .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
447     .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
448     Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
449     always distinct from the default loop. Unlike the default loop, it cannot
450     handle signal and child watchers, and attempts to do so will be greeted by
451     undefined behaviour (or a failed assertion if assertions are enabled).
452 root 1.9 .Sp
453     Example: try to create a event loop that uses epoll and nothing else.
454     .Sp
455     .Vb 3
456     \& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
457     \& if (!epoller)
458     \& fatal ("no epoll found here, maybe it hides under your chair");
459     .Ve
460 root 1.1 .IP "ev_default_destroy ()" 4
461     .IX Item "ev_default_destroy ()"
462     Destroys the default loop again (frees all memory and kernel state
463     etc.). This stops all registered event watchers (by not touching them in
464     any way whatsoever, although you cannot rely on this :).
465     .IP "ev_loop_destroy (loop)" 4
466     .IX Item "ev_loop_destroy (loop)"
467     Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
468     earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
469     .IP "ev_default_fork ()" 4
470     .IX Item "ev_default_fork ()"
471     This function reinitialises the kernel state for backends that have
472     one. Despite the name, you can call it anytime, but it makes most sense
473     after forking, in either the parent or child process (or both, but that
474     again makes little sense).
475     .Sp
476 root 1.5 You \fImust\fR call this function in the child process after forking if and
477     only if you want to use the event library in both processes. If you just
478     fork+exec, you don't have to call it.
479 root 1.1 .Sp
480     The function itself is quite fast and it's usually not a problem to call
481     it just in case after a fork. To make this easy, the function will fit in
482     quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR:
483     .Sp
484     .Vb 1
485     \& pthread_atfork (0, 0, ev_default_fork);
486     .Ve
487 root 1.6 .Sp
488     At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use
489     without calling this function, so if you force one of those backends you
490     do not need to care.
491 root 1.1 .IP "ev_loop_fork (loop)" 4
492     .IX Item "ev_loop_fork (loop)"
493     Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
494     \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
495     after fork, and how you do this is entirely your own problem.
496 root 1.6 .IP "unsigned int ev_backend (loop)" 4
497     .IX Item "unsigned int ev_backend (loop)"
498     Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
499 root 1.1 use.
500     .IP "ev_tstamp ev_now (loop)" 4
501     .IX Item "ev_tstamp ev_now (loop)"
502     Returns the current \*(L"event loop time\*(R", which is the time the event loop
503 root 1.9 received events and started processing them. This timestamp does not
504     change as long as callbacks are being processed, and this is also the base
505     time used for relative timers. You can treat it as the timestamp of the
506     event occuring (or more correctly, libev finding out about it).
507 root 1.1 .IP "ev_loop (loop, int flags)" 4
508     .IX Item "ev_loop (loop, int flags)"
509     Finally, this is it, the event handler. This function usually is called
510     after you initialised all your watchers and you want to start handling
511     events.
512     .Sp
513 root 1.8 If the flags argument is specified as \f(CW0\fR, it will not return until
514     either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
515 root 1.1 .Sp
516 root 1.9 Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than
517     relying on all watchers to be stopped when deciding when a program has
518     finished (especially in interactive programs), but having a program that
519     automatically loops as long as it has to and no longer by virtue of
520     relying on its watchers stopping correctly is a thing of beauty.
521     .Sp
522 root 1.1 A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
523     those events and any outstanding ones, but will not block your process in
524     case there are no events and will return after one iteration of the loop.
525     .Sp
526     A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if
527     neccessary) and will handle those and any outstanding ones. It will block
528     your process until at least one new event arrives, and will return after
529 root 1.8 one iteration of the loop. This is useful if you are waiting for some
530     external event in conjunction with something not expressible using other
531     libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
532     usually a better approach for this kind of thing.
533     .Sp
534     Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
535     .Sp
536     .Vb 18
537     \& * If there are no active watchers (reference count is zero), return.
538     \& - Queue prepare watchers and then call all outstanding watchers.
539     \& - If we have been forked, recreate the kernel state.
540     \& - Update the kernel state with all outstanding changes.
541     \& - Update the "event loop time".
542     \& - Calculate for how long to block.
543     \& - Block the process, waiting for any events.
544     \& - Queue all outstanding I/O (fd) events.
545     \& - Update the "event loop time" and do time jump handling.
546     \& - Queue all outstanding timers.
547     \& - Queue all outstanding periodics.
548     \& - If no events are pending now, queue all idle watchers.
549     \& - Queue all check watchers.
550     \& - Call all queued watchers in reverse order (i.e. check watchers first).
551     \& Signals and child watchers are implemented as I/O watchers, and will
552     \& be handled here by queueing them when their watcher gets executed.
553     \& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
554     \& were used, return, otherwise continue with step *.
555 root 1.2 .Ve
556 root 1.9 .Sp
557     Example: queue some jobs and then loop until no events are outsanding
558     anymore.
559     .Sp
560     .Vb 4
561     \& ... queue jobs here, make sure they register event watchers as long
562     \& ... as they still have work to do (even an idle watcher will do..)
563     \& ev_loop (my_loop, 0);
564     \& ... jobs done. yeah!
565     .Ve
566 root 1.1 .IP "ev_unloop (loop, how)" 4
567     .IX Item "ev_unloop (loop, how)"
568     Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
569     has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
570     \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or
571     \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return.
572     .IP "ev_ref (loop)" 4
573     .IX Item "ev_ref (loop)"
574     .PD 0
575     .IP "ev_unref (loop)" 4
576     .IX Item "ev_unref (loop)"
577     .PD
578     Ref/unref can be used to add or remove a reference count on the event
579     loop: Every watcher keeps one reference, and as long as the reference
580     count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have
581     a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from
582     returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For
583     example, libev itself uses this for its internal signal pipe: It is not
584     visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
585     no event watchers registered by it are active. It is also an excellent
586     way to do this for generic recurring timers or from within third-party
587     libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
588 root 1.9 .Sp
589     Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
590     running when nothing else is active.
591     .Sp
592     .Vb 4
593     \& struct dv_signal exitsig;
594     \& ev_signal_init (&exitsig, sig_cb, SIGINT);
595     \& ev_signal_start (myloop, &exitsig);
596     \& evf_unref (myloop);
597     .Ve
598     .Sp
599     Example: for some weird reason, unregister the above signal handler again.
600     .Sp
601     .Vb 2
602     \& ev_ref (myloop);
603     \& ev_signal_stop (myloop, &exitsig);
604     .Ve
605 root 1.1 .SH "ANATOMY OF A WATCHER"
606     .IX Header "ANATOMY OF A WATCHER"
607     A watcher is a structure that you create and register to record your
608     interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
609     become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
610     .PP
611     .Vb 5
612     \& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
613     \& {
614     \& ev_io_stop (w);
615     \& ev_unloop (loop, EVUNLOOP_ALL);
616     \& }
617     .Ve
618     .PP
619     .Vb 6
620     \& struct ev_loop *loop = ev_default_loop (0);
621     \& struct ev_io stdin_watcher;
622     \& ev_init (&stdin_watcher, my_cb);
623     \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
624     \& ev_io_start (loop, &stdin_watcher);
625     \& ev_loop (loop, 0);
626     .Ve
627     .PP
628     As you can see, you are responsible for allocating the memory for your
629     watcher structures (and it is usually a bad idea to do this on the stack,
630     although this can sometimes be quite valid).
631     .PP
632     Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init
633     (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This
634     callback gets invoked each time the event occurs (or, in the case of io
635     watchers, each time the event loop detects that the file descriptor given
636     is readable and/or writable).
637     .PP
638     Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro
639     with arguments specific to this watcher type. There is also a macro
640     to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init
641     (watcher *, callback, ...)\*(C'\fR.
642     .PP
643     To make the watcher actually watch out for events, you have to start it
644     with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher
645     *)\*(C'\fR), and you can stop watching for events at any time by calling the
646     corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
647     .PP
648     As long as your watcher is active (has been started but not stopped) you
649     must not touch the values stored in it. Most specifically you must never
650 root 1.11 reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
651 root 1.1 .PP
652     Each and every callback receives the event loop pointer as first, the
653     registered watcher structure as second, and a bitset of received events as
654     third argument.
655     .PP
656     The received events usually include a single bit per event type received
657     (you can receive multiple events at the same time). The possible bit masks
658     are:
659     .ie n .IP """EV_READ""" 4
660     .el .IP "\f(CWEV_READ\fR" 4
661     .IX Item "EV_READ"
662     .PD 0
663     .ie n .IP """EV_WRITE""" 4
664     .el .IP "\f(CWEV_WRITE\fR" 4
665     .IX Item "EV_WRITE"
666     .PD
667     The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or
668     writable.
669     .ie n .IP """EV_TIMEOUT""" 4
670     .el .IP "\f(CWEV_TIMEOUT\fR" 4
671     .IX Item "EV_TIMEOUT"
672     The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out.
673     .ie n .IP """EV_PERIODIC""" 4
674     .el .IP "\f(CWEV_PERIODIC\fR" 4
675     .IX Item "EV_PERIODIC"
676     The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out.
677     .ie n .IP """EV_SIGNAL""" 4
678     .el .IP "\f(CWEV_SIGNAL\fR" 4
679     .IX Item "EV_SIGNAL"
680     The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
681     .ie n .IP """EV_CHILD""" 4
682     .el .IP "\f(CWEV_CHILD\fR" 4
683     .IX Item "EV_CHILD"
684     The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
685     .ie n .IP """EV_IDLE""" 4
686     .el .IP "\f(CWEV_IDLE\fR" 4
687     .IX Item "EV_IDLE"
688     The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
689     .ie n .IP """EV_PREPARE""" 4
690     .el .IP "\f(CWEV_PREPARE\fR" 4
691     .IX Item "EV_PREPARE"
692     .PD 0
693     .ie n .IP """EV_CHECK""" 4
694     .el .IP "\f(CWEV_CHECK\fR" 4
695     .IX Item "EV_CHECK"
696     .PD
697     All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_loop\*(C'\fR starts
698     to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after
699     \&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
700     received events. Callbacks of both watcher types can start and stop as
701     many watchers as they want, and all of them will be taken into account
702     (for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
703     \&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
704     .ie n .IP """EV_ERROR""" 4
705     .el .IP "\f(CWEV_ERROR\fR" 4
706     .IX Item "EV_ERROR"
707     An unspecified error has occured, the watcher has been stopped. This might
708     happen because the watcher could not be properly started because libev
709     ran out of memory, a file descriptor was found to be closed or any other
710     problem. You best act on it by reporting the problem and somehow coping
711     with the watcher being stopped.
712     .Sp
713     Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
714     for example it might indicate that a fd is readable or writable, and if
715     your callbacks is well-written it can just attempt the operation and cope
716     with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
717     programs, though, so beware.
718 root 1.11 .Sh "\s-1SUMMARY\s0 \s-1OF\s0 \s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
719     .IX Subsection "SUMMARY OF GENERIC WATCHER FUNCTIONS"
720     In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
721     e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers.
722     .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
723     .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
724     .IX Item "ev_init (ev_TYPE *watcher, callback)"
725     This macro initialises the generic portion of a watcher. The contents
726     of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
727     the generic parts of the watcher are initialised, you \fIneed\fR to call
728     the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
729     type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
730     which rolls both calls into one.
731     .Sp
732     You can reinitialise a watcher at any time as long as it has been stopped
733     (or never started) and there are no pending events outstanding.
734     .Sp
735     The callbakc is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
736     int revents)\*(C'\fR.
737     .ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
738     .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
739     .IX Item "ev_TYPE_set (ev_TYPE *, [args])"
740     This macro initialises the type-specific parts of a watcher. You need to
741     call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
742     call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
743     macro on a watcher that is active (it can be pending, however, which is a
744     difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
745     .Sp
746     Although some watcher types do not have type-specific arguments
747     (e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
748     .ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
749     .el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
750     .IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
751     This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
752     calls into a single call. This is the most convinient method to initialise
753     a watcher. The same limitations apply, of course.
754     .ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
755     .el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
756     .IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
757     Starts (activates) the given watcher. Only active watchers will receive
758     events. If the watcher is already active nothing will happen.
759     .ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
760     .el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
761     .IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
762     Stops the given watcher again (if active) and clears the pending
763     status. It is possible that stopped watchers are pending (for example,
764     non-repeating timers are being stopped when they become pending), but
765     \&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
766     you want to free or reuse the memory used by the watcher it is therefore a
767     good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
768     .IP "bool ev_is_active (ev_TYPE *watcher)" 4
769     .IX Item "bool ev_is_active (ev_TYPE *watcher)"
770     Returns a true value iff the watcher is active (i.e. it has been started
771     and not yet been stopped). As long as a watcher is active you must not modify
772     it.
773     .IP "bool ev_is_pending (ev_TYPE *watcher)" 4
774     .IX Item "bool ev_is_pending (ev_TYPE *watcher)"
775     Returns a true value iff the watcher is pending, (i.e. it has outstanding
776     events but its callback has not yet been invoked). As long as a watcher
777     is pending (but not active) you must not call an init function on it (but
778     \&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
779     libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
780     .IP "callback = ev_cb (ev_TYPE *watcher)" 4
781     .IX Item "callback = ev_cb (ev_TYPE *watcher)"
782     Returns the callback currently set on the watcher.
783     .IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
784     .IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
785     Change the callback. You can change the callback at virtually any time
786     (modulo threads).
787 root 1.1 .Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
788     .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
789     Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
790     and read at any time, libev will completely ignore it. This can be used
791     to associate arbitrary data with your watcher. If you need more data and
792     don't want to allocate memory and store a pointer to it in that data
793     member, you can also \*(L"subclass\*(R" the watcher type and provide your own
794     data:
795     .PP
796     .Vb 7
797     \& struct my_io
798     \& {
799     \& struct ev_io io;
800     \& int otherfd;
801     \& void *somedata;
802     \& struct whatever *mostinteresting;
803     \& }
804     .Ve
805     .PP
806     And since your callback will be called with a pointer to the watcher, you
807     can cast it back to your own type:
808     .PP
809     .Vb 5
810     \& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
811     \& {
812     \& struct my_io *w = (struct my_io *)w_;
813     \& ...
814     \& }
815     .Ve
816     .PP
817     More interesting and less C\-conformant ways of catsing your callback type
818     have been omitted....
819     .SH "WATCHER TYPES"
820     .IX Header "WATCHER TYPES"
821     This section describes each watcher in detail, but will not repeat
822     information given in the last section.
823     .ie n .Sh """ev_io"" \- is this file descriptor readable or writable"
824     .el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable"
825     .IX Subsection "ev_io - is this file descriptor readable or writable"
826     I/O watchers check whether a file descriptor is readable or writable
827     in each iteration of the event loop (This behaviour is called
828     level-triggering because you keep receiving events as long as the
829     condition persists. Remember you can stop the watcher if you don't want to
830     act on the event and neither want to receive future events).
831     .PP
832     In general you can register as many read and/or write event watchers per
833     fd as you want (as long as you don't confuse yourself). Setting all file
834     descriptors to non-blocking mode is also usually a good idea (but not
835     required if you know what you are doing).
836     .PP
837     You have to be careful with dup'ed file descriptors, though. Some backends
838     (the linux epoll backend is a notable example) cannot handle dup'ed file
839     descriptors correctly if you register interest in two or more fds pointing
840     to the same underlying file/socket etc. description (that is, they share
841     the same underlying \*(L"file open\*(R").
842     .PP
843     If you must do this, then force the use of a known-to-be-good backend
844 root 1.6 (at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
845     \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
846 root 1.1 .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
847     .IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
848     .PD 0
849     .IP "ev_io_set (ev_io *, int fd, int events)" 4
850     .IX Item "ev_io_set (ev_io *, int fd, int events)"
851     .PD
852     Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive
853     events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ |
854     EV_WRITE\*(C'\fR to receive the given events.
855 root 1.7 .Sp
856     Please note that most of the more scalable backend mechanisms (for example
857     epoll and solaris ports) can result in spurious readyness notifications
858     for file descriptors, so you practically need to use non-blocking I/O (and
859     treat callback invocation as hint only), or retest separately with a safe
860     interface before doing I/O (XLib can do this), or force the use of either
861     \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this
862     problem. Also note that it is quite easy to have your callback invoked
863     when the readyness condition is no longer valid even when employing
864     typical ways of handling events, so its a good idea to use non-blocking
865     I/O unconditionally.
866 root 1.9 .PP
867     Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
868     readable, but only once. Since it is likely line\-buffered, you could
869     attempt to read a whole line in the callback:
870     .PP
871     .Vb 6
872     \& static void
873     \& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
874     \& {
875     \& ev_io_stop (loop, w);
876     \& .. read from stdin here (or from w->fd) and haqndle any I/O errors
877     \& }
878     .Ve
879     .PP
880     .Vb 6
881     \& ...
882     \& struct ev_loop *loop = ev_default_init (0);
883     \& struct ev_io stdin_readable;
884     \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
885     \& ev_io_start (loop, &stdin_readable);
886     \& ev_loop (loop, 0);
887     .Ve
888 root 1.1 .ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts"
889     .el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts"
890     .IX Subsection "ev_timer - relative and optionally recurring timeouts"
891     Timer watchers are simple relative timers that generate an event after a
892     given time, and optionally repeating in regular intervals after that.
893     .PP
894     The timers are based on real time, that is, if you register an event that
895     times out after an hour and you reset your system clock to last years
896     time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because
897 root 1.2 detecting time jumps is hard, and some inaccuracies are unavoidable (the
898 root 1.1 monotonic clock option helps a lot here).
899     .PP
900     The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR
901     time. This is usually the right thing as this timestamp refers to the time
902 root 1.2 of the event triggering whatever timeout you are modifying/starting. If
903     you suspect event processing to be delayed and you \fIneed\fR to base the timeout
904 root 1.1 on the current time, use something like this to adjust for this:
905     .PP
906     .Vb 1
907     \& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
908     .Ve
909 root 1.2 .PP
910     The callback is guarenteed to be invoked only when its timeout has passed,
911     but if multiple timers become ready during the same loop iteration then
912     order of execution is undefined.
913 root 1.1 .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
914     .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
915     .PD 0
916     .IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
917     .IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
918     .PD
919     Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR is
920     \&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the
921     timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds
922     later, again, and again, until stopped manually.
923     .Sp
924     The timer itself will do a best-effort at avoiding drift, that is, if you
925     configure a timer to trigger every 10 seconds, then it will trigger at
926     exactly 10 second intervals. If, however, your program cannot keep up with
927     the timer (because it takes longer than those 10 seconds to do stuff) the
928     timer will not fire more than once per event loop iteration.
929     .IP "ev_timer_again (loop)" 4
930     .IX Item "ev_timer_again (loop)"
931     This will act as if the timer timed out and restart it again if it is
932     repeating. The exact semantics are:
933     .Sp
934     If the timer is started but nonrepeating, stop it.
935     .Sp
936     If the timer is repeating, either start it if necessary (with the repeat
937     value), or reset the running timer to the repeat value.
938     .Sp
939     This sounds a bit complicated, but here is a useful and typical
940     example: Imagine you have a tcp connection and you want a so-called idle
941     timeout, that is, you want to be called when there have been, say, 60
942     seconds of inactivity on the socket. The easiest way to do this is to
943     configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each
944     time you successfully read or write some data. If you go into an idle
945     state where you do not expect data to travel on the socket, you can stop
946     the timer, and again will automatically restart it if need be.
947 root 1.9 .PP
948     Example: create a timer that fires after 60 seconds.
949     .PP
950     .Vb 5
951     \& static void
952     \& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
953     \& {
954     \& .. one minute over, w is actually stopped right here
955     \& }
956     .Ve
957     .PP
958     .Vb 3
959     \& struct ev_timer mytimer;
960     \& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
961     \& ev_timer_start (loop, &mytimer);
962     .Ve
963     .PP
964     Example: create a timeout timer that times out after 10 seconds of
965     inactivity.
966     .PP
967     .Vb 5
968     \& static void
969     \& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
970     \& {
971     \& .. ten seconds without any activity
972     \& }
973     .Ve
974     .PP
975     .Vb 4
976     \& struct ev_timer mytimer;
977     \& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
978     \& ev_timer_again (&mytimer); /* start timer */
979     \& ev_loop (loop, 0);
980     .Ve
981     .PP
982     .Vb 3
983     \& // and in some piece of code that gets executed on any "activity":
984     \& // reset the timeout to start ticking again at 10 seconds
985     \& ev_timer_again (&mytimer);
986     .Ve
987 root 1.1 .ie n .Sh """ev_periodic"" \- to cron or not to cron"
988     .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron"
989     .IX Subsection "ev_periodic - to cron or not to cron"
990     Periodic watchers are also timers of a kind, but they are very versatile
991     (and unfortunately a bit complex).
992     .PP
993     Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
994     but on wallclock time (absolute time). You can tell a periodic watcher
995     to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
996     periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()
997     + 10.>) and then reset your system clock to the last year, then it will
998     take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
999     roughly 10 seconds later and of course not if you reset your system time
1000     again).
1001     .PP
1002     They can also be used to implement vastly more complex timers, such as
1003     triggering an event on eahc midnight, local time.
1004 root 1.2 .PP
1005     As with timers, the callback is guarenteed to be invoked only when the
1006     time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
1007     during the same loop iteration then order of execution is undefined.
1008 root 1.1 .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
1009     .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
1010     .PD 0
1011     .IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
1012     .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
1013     .PD
1014     Lots of arguments, lets sort it out... There are basically three modes of
1015     operation, and we will explain them from simplest to complex:
1016     .RS 4
1017     .IP "* absolute timer (interval = reschedule_cb = 0)" 4
1018     .IX Item "absolute timer (interval = reschedule_cb = 0)"
1019     In this configuration the watcher triggers an event at the wallclock time
1020     \&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
1021     that is, if it is to be run at January 1st 2011 then it will run when the
1022     system time reaches or surpasses this time.
1023     .IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4
1024     .IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)"
1025     In this mode the watcher will always be scheduled to time out at the next
1026     \&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless
1027     of any time jumps.
1028     .Sp
1029     This can be used to create timers that do not drift with respect to system
1030     time:
1031     .Sp
1032     .Vb 1
1033     \& ev_periodic_set (&periodic, 0., 3600., 0);
1034     .Ve
1035     .Sp
1036     This doesn't mean there will always be 3600 seconds in between triggers,
1037     but only that the the callback will be called when the system time shows a
1038     full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible
1039     by 3600.
1040     .Sp
1041     Another way to think about it (for the mathematically inclined) is that
1042     \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
1043     time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
1044     .IP "* manual reschedule mode (reschedule_cb = callback)" 4
1045     .IX Item "manual reschedule mode (reschedule_cb = callback)"
1046     In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
1047     ignored. Instead, each time the periodic watcher gets scheduled, the
1048     reschedule callback will be called with the watcher as first, and the
1049     current time as second argument.
1050     .Sp
1051     \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
1052     ever, or make any event loop modifications\fR. If you need to stop it,
1053     return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
1054     starting a prepare watcher).
1055     .Sp
1056     Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1057     ev_tstamp now)\*(C'\fR, e.g.:
1058     .Sp
1059     .Vb 4
1060     \& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1061     \& {
1062     \& return now + 60.;
1063     \& }
1064     .Ve
1065     .Sp
1066     It must return the next time to trigger, based on the passed time value
1067     (that is, the lowest time value larger than to the second argument). It
1068     will usually be called just before the callback will be triggered, but
1069     might be called at other times, too.
1070     .Sp
1071     \&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the
1072     passed \f(CI\*(C`now\*(C'\fI value\fR. Not even \f(CW\*(C`now\*(C'\fR itself will do, it \fImust\fR be larger.
1073     .Sp
1074     This can be used to create very complex timers, such as a timer that
1075     triggers on each midnight, local time. To do this, you would calculate the
1076     next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How
1077     you do this is, again, up to you (but it is not trivial, which is the main
1078     reason I omitted it as an example).
1079     .RE
1080     .RS 4
1081     .RE
1082     .IP "ev_periodic_again (loop, ev_periodic *)" 4
1083     .IX Item "ev_periodic_again (loop, ev_periodic *)"
1084     Simply stops and restarts the periodic watcher again. This is only useful
1085     when you changed some parameters or the reschedule callback would return
1086     a different time than the last time it was called (e.g. in a crond like
1087     program when the crontabs have changed).
1088 root 1.9 .PP
1089     Example: call a callback every hour, or, more precisely, whenever the
1090     system clock is divisible by 3600. The callback invocation times have
1091     potentially a lot of jittering, but good long-term stability.
1092     .PP
1093     .Vb 5
1094     \& static void
1095     \& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1096     \& {
1097     \& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1098     \& }
1099     .Ve
1100     .PP
1101     .Vb 3
1102     \& struct ev_periodic hourly_tick;
1103     \& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1104     \& ev_periodic_start (loop, &hourly_tick);
1105     .Ve
1106     .PP
1107     Example: the same as above, but use a reschedule callback to do it:
1108     .PP
1109     .Vb 1
1110     \& #include <math.h>
1111     .Ve
1112     .PP
1113     .Vb 5
1114     \& static ev_tstamp
1115     \& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1116     \& {
1117     \& return fmod (now, 3600.) + 3600.;
1118     \& }
1119     .Ve
1120     .PP
1121     .Vb 1
1122     \& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1123     .Ve
1124     .PP
1125     Example: call a callback every hour, starting now:
1126     .PP
1127     .Vb 4
1128     \& struct ev_periodic hourly_tick;
1129     \& ev_periodic_init (&hourly_tick, clock_cb,
1130     \& fmod (ev_now (loop), 3600.), 3600., 0);
1131     \& ev_periodic_start (loop, &hourly_tick);
1132     .Ve
1133 root 1.1 .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled"
1134     .el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled"
1135     .IX Subsection "ev_signal - signal me when a signal gets signalled"
1136     Signal watchers will trigger an event when the process receives a specific
1137     signal one or more times. Even though signals are very asynchronous, libev
1138     will try it's best to deliver signals synchronously, i.e. as part of the
1139     normal event processing, like any other event.
1140     .PP
1141     You can configure as many watchers as you like per signal. Only when the
1142     first watcher gets started will libev actually register a signal watcher
1143     with the kernel (thus it coexists with your own signal handlers as long
1144     as you don't register any with libev). Similarly, when the last signal
1145     watcher for a signal is stopped libev will reset the signal handler to
1146     \&\s-1SIG_DFL\s0 (regardless of what it was set to before).
1147     .IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1148     .IX Item "ev_signal_init (ev_signal *, callback, int signum)"
1149     .PD 0
1150     .IP "ev_signal_set (ev_signal *, int signum)" 4
1151     .IX Item "ev_signal_set (ev_signal *, int signum)"
1152     .PD
1153     Configures the watcher to trigger on the given signal number (usually one
1154     of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1155     .ie n .Sh """ev_child"" \- wait for pid status changes"
1156     .el .Sh "\f(CWev_child\fP \- wait for pid status changes"
1157     .IX Subsection "ev_child - wait for pid status changes"
1158     Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1159     some child status changes (most typically when a child of yours dies).
1160     .IP "ev_child_init (ev_child *, callback, int pid)" 4
1161     .IX Item "ev_child_init (ev_child *, callback, int pid)"
1162     .PD 0
1163     .IP "ev_child_set (ev_child *, int pid)" 4
1164     .IX Item "ev_child_set (ev_child *, int pid)"
1165     .PD
1166     Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or
1167     \&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
1168     at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
1169     the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
1170     \&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
1171     process causing the status change.
1172 root 1.9 .PP
1173     Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1174     .PP
1175     .Vb 5
1176     \& static void
1177     \& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1178     \& {
1179     \& ev_unloop (loop, EVUNLOOP_ALL);
1180     \& }
1181     .Ve
1182     .PP
1183     .Vb 3
1184     \& struct ev_signal signal_watcher;
1185     \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1186     \& ev_signal_start (loop, &sigint_cb);
1187     .Ve
1188 root 1.1 .ie n .Sh """ev_idle"" \- when you've got nothing better to do"
1189     .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do"
1190     .IX Subsection "ev_idle - when you've got nothing better to do"
1191     Idle watchers trigger events when there are no other events are pending
1192     (prepare, check and other idle watchers do not count). That is, as long
1193     as your process is busy handling sockets or timeouts (or even signals,
1194     imagine) it will not be triggered. But when your process is idle all idle
1195     watchers are being called again and again, once per event loop iteration \-
1196     until stopped, that is, or your process receives more events and becomes
1197     busy.
1198     .PP
1199     The most noteworthy effect is that as long as any idle watchers are
1200     active, the process will not block when waiting for new events.
1201     .PP
1202     Apart from keeping your process non-blocking (which is a useful
1203     effect on its own sometimes), idle watchers are a good place to do
1204     \&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the
1205     event loop has handled all outstanding events.
1206     .IP "ev_idle_init (ev_signal *, callback)" 4
1207     .IX Item "ev_idle_init (ev_signal *, callback)"
1208     Initialises and configures the idle watcher \- it has no parameters of any
1209     kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1210     believe me.
1211 root 1.9 .PP
1212     Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the
1213     callback, free it. Alos, use no error checking, as usual.
1214     .PP
1215     .Vb 7
1216     \& static void
1217     \& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1218     \& {
1219     \& free (w);
1220     \& // now do something you wanted to do when the program has
1221     \& // no longer asnything immediate to do.
1222     \& }
1223     .Ve
1224     .PP
1225     .Vb 3
1226     \& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1227     \& ev_idle_init (idle_watcher, idle_cb);
1228     \& ev_idle_start (loop, idle_cb);
1229     .Ve
1230 root 1.1 .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop"
1231     .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop"
1232     .IX Subsection "ev_prepare and ev_check - customise your event loop"
1233     Prepare and check watchers are usually (but not always) used in tandem:
1234     prepare watchers get invoked before the process blocks and check watchers
1235     afterwards.
1236     .PP
1237 root 1.10 Their main purpose is to integrate other event mechanisms into libev and
1238     their use is somewhat advanced. This could be used, for example, to track
1239     variable changes, implement your own watchers, integrate net-snmp or a
1240     coroutine library and lots more.
1241 root 1.1 .PP
1242     This is done by examining in each prepare call which file descriptors need
1243     to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
1244     them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
1245     provide just this functionality). Then, in the check watcher you check for
1246     any events that occured (by checking the pending status of all watchers
1247     and stopping them) and call back into the library. The I/O and timer
1248     callbacks will never actually be called (but must be valid nevertheless,
1249     because you never know, you know?).
1250     .PP
1251     As another example, the Perl Coro module uses these hooks to integrate
1252     coroutines into libev programs, by yielding to other active coroutines
1253     during each prepare and only letting the process block if no coroutines
1254     are ready to run (it's actually more complicated: it only runs coroutines
1255     with priority higher than or equal to the event loop and one coroutine
1256     of lower priority, but only once, using idle watchers to keep the event
1257     loop from blocking if lower-priority coroutines are active, thus mapping
1258     low-priority coroutines to idle/background tasks).
1259     .IP "ev_prepare_init (ev_prepare *, callback)" 4
1260     .IX Item "ev_prepare_init (ev_prepare *, callback)"
1261     .PD 0
1262     .IP "ev_check_init (ev_check *, callback)" 4
1263     .IX Item "ev_check_init (ev_check *, callback)"
1264     .PD
1265     Initialises and configures the prepare or check watcher \- they have no
1266     parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1267     macros, but using them is utterly, utterly and completely pointless.
1268 root 1.9 .PP
1269     Example: *TODO*.
1270 root 1.10 .ie n .Sh """ev_embed"" \- when one backend isn't enough"
1271     .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough"
1272     .IX Subsection "ev_embed - when one backend isn't enough"
1273     This is a rather advanced watcher type that lets you embed one event loop
1274 root 1.11 into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1275     loop, other types of watchers might be handled in a delayed or incorrect
1276     fashion and must not be used).
1277 root 1.10 .PP
1278     There are primarily two reasons you would want that: work around bugs and
1279     prioritise I/O.
1280     .PP
1281     As an example for a bug workaround, the kqueue backend might only support
1282     sockets on some platform, so it is unusable as generic backend, but you
1283     still want to make use of it because you have many sockets and it scales
1284     so nicely. In this case, you would create a kqueue-based loop and embed it
1285     into your default loop (which might use e.g. poll). Overall operation will
1286     be a bit slower because first libev has to poll and then call kevent, but
1287     at least you can use both at what they are best.
1288     .PP
1289     As for prioritising I/O: rarely you have the case where some fds have
1290     to be watched and handled very quickly (with low latency), and even
1291     priorities and idle watchers might have too much overhead. In this case
1292     you would put all the high priority stuff in one loop and all the rest in
1293     a second one, and embed the second one in the first.
1294     .PP
1295 root 1.11 As long as the watcher is active, the callback will be invoked every time
1296     there might be events pending in the embedded loop. The callback must then
1297     call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
1298     their callbacks (you could also start an idle watcher to give the embedded
1299     loop strictly lower priority for example). You can also set the callback
1300     to \f(CW0\fR, in which case the embed watcher will automatically execute the
1301     embedded loop sweep.
1302     .PP
1303 root 1.10 As long as the watcher is started it will automatically handle events. The
1304     callback will be invoked whenever some events have been handled. You can
1305     set the callback to \f(CW0\fR to avoid having to specify one if you are not
1306     interested in that.
1307     .PP
1308     Also, there have not currently been made special provisions for forking:
1309     when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
1310     but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
1311     yourself.
1312     .PP
1313     Unfortunately, not all backends are embeddable, only the ones returned by
1314     \&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1315     portable one.
1316     .PP
1317     So when you want to use this feature you will always have to be prepared
1318     that you cannot get an embeddable loop. The recommended way to get around
1319     this is to have a separate variables for your embeddable loop, try to
1320     create it, and if that fails, use the normal loop for everything:
1321     .PP
1322     .Vb 3
1323     \& struct ev_loop *loop_hi = ev_default_init (0);
1324     \& struct ev_loop *loop_lo = 0;
1325     \& struct ev_embed embed;
1326     .Ve
1327     .PP
1328     .Vb 5
1329     \& // see if there is a chance of getting one that works
1330     \& // (remember that a flags value of 0 means autodetection)
1331     \& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1332     \& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1333     \& : 0;
1334     .Ve
1335     .PP
1336     .Vb 8
1337     \& // if we got one, then embed it, otherwise default to loop_hi
1338     \& if (loop_lo)
1339     \& {
1340     \& ev_embed_init (&embed, 0, loop_lo);
1341     \& ev_embed_start (loop_hi, &embed);
1342     \& }
1343     \& else
1344     \& loop_lo = loop_hi;
1345     .Ve
1346 root 1.11 .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1347     .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1348 root 1.10 .PD 0
1349 root 1.11 .IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1350     .IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
1351 root 1.10 .PD
1352 root 1.11 Configures the watcher to embed the given loop, which must be
1353     embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1354     invoked automatically, otherwise it is the responsibility of the callback
1355     to invoke it (it will continue to be called until the sweep has been done,
1356     if you do not want thta, you need to temporarily stop the embed watcher).
1357     .IP "ev_embed_sweep (loop, ev_embed *)" 4
1358     .IX Item "ev_embed_sweep (loop, ev_embed *)"
1359     Make a single, non-blocking sweep over the embedded loop. This works
1360     similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1361     apropriate way for embedded loops.
1362 root 1.1 .SH "OTHER FUNCTIONS"
1363     .IX Header "OTHER FUNCTIONS"
1364     There are some other functions of possible interest. Described. Here. Now.
1365     .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
1366     .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
1367     This function combines a simple timer and an I/O watcher, calls your
1368     callback on whichever event happens first and automatically stop both
1369     watchers. This is useful if you want to wait for a single event on an fd
1370     or timeout without having to allocate/configure/start/stop/free one or
1371     more watchers yourself.
1372     .Sp
1373     If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events
1374     is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and
1375     \&\f(CW\*(C`events\*(C'\fR set will be craeted and started.
1376     .Sp
1377     If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be
1378     started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and
1379     repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of
1380     dubious value.
1381     .Sp
1382     The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets
1383     passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of
1384     \&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR
1385     value passed to \f(CW\*(C`ev_once\*(C'\fR:
1386     .Sp
1387     .Vb 7
1388     \& static void stdin_ready (int revents, void *arg)
1389     \& {
1390     \& if (revents & EV_TIMEOUT)
1391     \& /* doh, nothing entered */;
1392     \& else if (revents & EV_READ)
1393     \& /* stdin might have data for us, joy! */;
1394     \& }
1395     .Ve
1396     .Sp
1397     .Vb 1
1398     \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1399     .Ve
1400 root 1.11 .IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
1401     .IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
1402 root 1.1 Feeds the given event set into the event loop, as if the specified event
1403     had happened for the specified watcher (which must be a pointer to an
1404     initialised but not necessarily started event watcher).
1405 root 1.11 .IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
1406     .IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
1407 root 1.1 Feed an event on the given fd, as if a file descriptor backend detected
1408     the given events it.
1409 root 1.11 .IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
1410     .IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
1411     Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
1412     loop!).
1413 root 1.1 .SH "LIBEVENT EMULATION"
1414     .IX Header "LIBEVENT EMULATION"
1415     Libev offers a compatibility emulation layer for libevent. It cannot
1416     emulate the internals of libevent, so here are some usage hints:
1417     .IP "* Use it by including <event.h>, as usual." 4
1418     .IX Item "Use it by including <event.h>, as usual."
1419     .PD 0
1420     .IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4
1421     .IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events."
1422     .IP "* Avoid using ev_flags and the EVLIST_*\-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private \s-1API\s0)." 4
1423     .IX Item "Avoid using ev_flags and the EVLIST_*-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private API)."
1424     .IP "* Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." 4
1425     .IX Item "Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field."
1426     .IP "* Other members are not supported." 4
1427     .IX Item "Other members are not supported."
1428     .IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
1429     .IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
1430     .PD
1431     .SH "\*(C+ SUPPORT"
1432     .IX Header " SUPPORT"
1433     \&\s-1TBD\s0.
1434     .SH "AUTHOR"
1435     .IX Header "AUTHOR"
1436     Marc Lehmann <libev@schmorp.de>.